Large scale data centers are a relatively new human artifact, and their organization and structure has evolved rapidly as the commercial opportunities they provide has expanded. Typical modern data centers are organized collections of clusters of hardware running collections of standard software packages, such as web servers database servers, etc., interconnected by high speed networking, routers, and firewalls. The task of organizing these machines, optimizing their configuration, debugging errors in their configuration, and installing and uninstalling software on the constituent machines is largely left to human operators.
Web services (e.g., software as a service “SaaS”) supported by data centers are also rapidly evolving (for example, a company might first offer a search service, and then an email service, and then a Map service, etc.). Many services are designed as “distributed” applications characterized by components that run on different machines, typically in communication via a network, such as the Internet. For example, a shift towards interactive Web 2.0 applications has led to development of truly distributed systems where code is written in different languages, runs on multiple machines, and interacts in complex ways. Today, many such applications are written in an ad-hoc manner, where the server and client-side functionality are developed at the same time—but separately and often in different programming languages—and subsequently combined. Distribution of multi-tier components can be complex and require significant resources to ensure proper operation, not to mention collection of information as to how an application performs, the number of users and other metrics that can impact overall cost (e.g., number of servers, bandwidth, number of I/Os, advertising revenue, etc.).
Various exemplary technologies described herein pertain to architectures and programming models that can facilitate access to a “cloud” of data centers, users and other entities.